Question

http://prntscr.com/kq8n8s @shadow

Answer 1

Which ones are you thinking?

Answer 2

I think the answer is either A or B. Not completely sure though.

Answer 3

What makes a test/study/experiment valid is whether or not it measures what it claims to measure, right?

Answer 4

That sounds good to me. Good vocab knowledge

Answer 5

So, do you agree that it's A?

Answer 6

Second opinion -- given that there was no correlation stated between cancer and stress, the claim "there is a relationship between cancer and sleep levels" has no merit.

So yes, A would be correct.